let arr1 = ['张三', '李四', '王五', '老六'];

// 返回的是数组的迭代器对象，可用通过.next()访问内部的值
// { value: 0, done: false }
let key = arr1.keys();
let value = arr1.values();
let entry = arr1.entries();
console.log(key);  // [0,1,2,3]
console.log(value);
console.log(entry);

console.log(key.next());
console.log(key.next());
console.log(key.next());
console.log(key.next());
console.log(key.next());